Pressure responsive device having improved means for calibration

ABSTRACT

A pressure responsive device comprises a first chamber having a port sealed from a second chamber by a pressure responsive snap acting diaphragm. At pressures above an actuation pressure the diaphragm snaps from a first configuration to a second opposite configuration causing a motion transfer pin to move and actuate an electrical switch. The diaphragm snaps back to the first configuration when pressure decreases to a deactuation pressure, different than the actuation pressure, thereby permitting deactuation of the switch. A special diaphragm support is provided to enable calibration of both the actuation and the deactuation pressure independently of one another.

United States Patent [191 Fiore June 11, 1974 PRESSURE RESPONSIVE DEVICEHAVING IMPROVED MEANS FOR CALIBRATION Dallas, Tex.

[22] Filed: Dec. 26, 1972 [21] App]. N0.: 317,905

[52] U.S. Cl. 200/83 S, 200/83 P, 92/132 [51] Int. Cl. I-I0lh 35/34 [58]Field of Search..... 200/83 S, 83 R, 83 W, 83 J, 200/83 P, 83 U;327/323, 319; 92/132, 13, 101

Primary Examiner-Robert K. Schaefer Assistant ExaminerR. A. VanderhyeAttorney, Agent, or Firm-John A. Haug; James P.

McAndrews; Edward J. Connors, Jr.

[ 5 7 ABSTRACT A pressure responsive device comprises a first chamberhaving a port sealed from a second chamber by a pressure responsive snapacting diaphragm. At pressures above an actuation pressure the diaphragmsnaps from a first configuration to a second opposite configurationcausing a motion transfer pin to move and actuate an electrical switch.The diaphragm snaps back to the first configuration when pressuredecreases to a deactuation pressure, different than the actuationpressure, thereby permitting deactuation of the switch. A specialdiaphragm support is provided to enable calibration of both theactuation and the deactuation pressure independently of one another.

10 Claims, 2 Drawing Figures PRESSURE RESPONSIVE DEVICE HAVING IMPROVEDMEANS FOR CALIBRATION This invention relates generally to pressureresponsive switches and more particularly to a pressure responsiveswitch having improved means for calibration.

BACKGROUND OF THE INVENTION Devices are known for opening and closing anelectrical circuit or an electrical switch in response to changes invalues of pressure by admitting pressure to one side of a snap actingdiaphragm causing it to snap from a first configuration to a secondconfiguration at a predetermined value of pressure or actuation pressureand return at another value of pressure or deactuation pressure. Thedifference between'these values of pressure is called the pressuredifferential of the diaphragm of the device.

In U.S. Pat. No. 3,378,656 issued Apr. 16, 1968 assigned to the assigneeof the instant invention, it is taught that by altering the slope of theperipheral portion of the snap acting diaphragm the pressuredifferential of the diaphragm can be adjusted. It has been found thatsuch alteration affects primarily the actuation pressure of thediaphragm. As described in the patent the diaphragm is attached alongits periphery to a ring. The ring is deformed, as by forcing a toolmember against it in order to change the slope of the outer peripheraledge of the diaphragm. In U.S. Pat. No. 3,584,168 issued June 8, 1971,also assigned to the assignee of this invention, it is taught that byproviding an annular shaped calibration stop member the pressuredifferential of the diaphragm can also be adjusted. The adjustmenteffected by using this member is the deactuation pressure. As describedin the latter patent a snap acting diaphragm is attached along itsperiphery to the periphery of the annular calibration stop member. Tolower the deactuation pressure sufficient pressure is brought to bearagainst the diaphragm to deform the calibration-stop member. Converselyto raise the deactuation pressure a force is exerted, as by a tool,against the calibration-stop member deforming it toward the diaphragm.The force required to deform the calibration-stop member issubstantially greater than any forces to which the diaphragm will besubjected during operation as a pressure responsive device. While bothof these approaches are effective a problem exists when it is desired toadjustboth the actuation and deactuation pressures. That is adjustmentof the slope of the outer peripheral edge of the diaphragm tends toaffect the position of the calibration-stop member and hence thedeactuation pressure while adjustment of the calibration-stop membertends to affect the slope of the outer peripheral edge and hence theactuation pressure. Thus in order to obtain specific actuation,deactuation pressures it is frequently necessary for the personcalibrating the device to cycle back and forth between the twoadjustments and finally to make a judgment adjustment to obtain therequired calibration.

SUMMARY OF THE INVENTION Thus in order to reduce assembly costs and makethe device amenable to quick and accurate calibration of both theactuation and deactuation pressures the instant invention provides aspecial calibration-stop member having a portion used for adjustment ofthe actuation pressure, another portion used for adjustment of thedeactuation pressure and means to isolate the two portions from eachother. Essentially the improved calibration stop member comprises arelatively rigid annular flange joined to a variable cone center portionby an isolation land and groove which serve as a stress concentrator.

Thus among the several objects of the invention may be noted theprovision of an improved pressure responsive device in which theactuation and deactuation pressures can be independently adjusted.Another provision is the provision of a pressure responsive device whichis less' expensive to produce than prior art de-' vices having the samecalibration tolerances, a device which can be readily produced on a highvolume basis, one which can be easily calibrated by automated processesand one which is reliable and has a long usable life.

The invention accordingly comprises the constructions hereinafterdescribed, the scope of the invention being indicated in the followingclaims.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings, in whichtwo of the various possible embodiments of the invention areillustrated,

FIG. 1 is a front cross section taken through the center of a pressureresponsive device made in accordance with the invention, and

FIG. 2 is a front cross section taken through the center of an alternatecalibration-stop member useful in the FIG. I embodiment.

Dimensions of certain of the parts as shown in the drawings may havebeenmodified to illustrate the invention with more clarity.

Corresponding reference characters indicate corresponding partsthroughout the several views of the drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1 numeral 10 representsa switch made in accordance with the invention. A housing 12 receives ahub portion 14 which in turn slidingly receives a motion transfer pin 16in a centrally located bore extending through the hub. Hub 14 is joinedto housing 12 by collar member 13 crimped thereto. Members 18 and 20extend through apertures in bottom wall 22 of housing 12 lockingterminals 24, 26 as by staking in electrical connection therewith.Member 18 has a portion 19 extending laterally therefrom into the switchcavity 28 which serves as a stationary contact. Member 18 may beprovided with a layer of material having especially high electricalconductivity characteristics such as copper or silver. A movable contactarm 30 formed of an electrically conductive material having good springcharacteristics such as beryllium nickel cantilever mounted to member 20in any convenient manner by riveting at 32. Contact 34 is mounted on thefree distal end and is adapted to move into and out of engagement withportion 19 in response to the position of pin 16. A snap acting disc 36,either monometallic or multimetallic is positioned adjacent an end ofpin 16 and is adapted to change from the configuration shown in FIG. 1to an over center configuration in which it biases pin 16 downwardly andwith it movable arm 30 thereby opening the circuit through terminals 24,26. Disc 36 is supported on calibration member 38 and is sandwichedbetween member 38 and cover 40. Preferably these members and collar 13are sealed at their marginal periphery as by heliarc welding along theirperiphery as indicated at 42. It will be understood that other means maybe employed to seal the diaphragm member from the pressure chamber as byclamping.

Port fitting 44 is provided with boss 46 which is received in a matingaperture in cover 40 and has a bore 48 therein for reception of pressure(or vacuum). Also shown is an adjusting screw 50 also having alongitudinally extending bore 52 and a spring seat 54 for reception ofspring 56 which extends from the spring seat 54 to disc 36. Spring 56and adjusting screw 50 are optional and may be used if it is desirableto narrow the pressure differential.

Housing 58 has an annular seat 60 which receives the outer peripheralportion 64 of cover 40, disc 38, member 38 and collar 13. Housing 58 isprovided with apertures 66, 68 for reception therethrough of insulatedwires 70, 72 which are connected respectively to terminals 24, 26 in anysuitable manner as by crimping. Housing 58 is then back filled withsuitable electrically a insulative material such as potting material 59.

Calibration-stop member 38 comprises a first annular outer portion 74, asecond annular inner cone portion 76 and joined thereto by land 78formed with a groove 80 therebetween which acts as an isolation means.Land 78 extends intermediate the bottom surface of outer portion 74 andthe junction with inner portion 76. Bore 77 is provided in member 38 topermit pin 16 to pass therethrough.

Member 38 is formed of a material such as AISI type 304 Stainless Steeland is hydrogen annealed after forming to a Rockwell superficialhardness of (15-T) 73-90. This permits permanent deformation of member38 as desired. It should be noted that for member 38 to function asintended no portion of 76 can be above the level of portion 74.

Thus the device may be assembled by first forming a subassembly bywelding together cover 40, diaphragm 36, calibration-stop member 38 andcollar 13. At this point the actuation pressure rating can be adjustedby permanently deforming the outer periphery margin of member 38 byusing an appropriate tool, until the slope of the outer peripheralmargin of diaphragm 36 is such that the diaphragm snaps at the desiredactuation pressure. Once this is accomplished the deactuation pressurerating can be adjusted by introducing through cover 40 sufficientpressure to deform portion 76 of member 38 changing the angle of thisconical portion to the desired amount when the diaphragm will snap backto its original configuration at the desired deactuation pressure. Thethickness of portion 76 is such that a pressure substantially above anyoperating pressures to which the device will be subjected to in use as aswitch is required to deform the portion. Due to the existence of groove80 and land 78 the stresses created upon deformation of portion 76 areconcentrated in land 78 and portion 74 is unaffected by thisdeformation. Thus each pressure setting can be carefully, accurately andindependently adjusted. Another advantage offered by use of the grooveis that it standardizes the tangent line of contact between the dishedportion of the diaphragm and calibration-stop member. Without the groovethe tangent line could vary around the periphery of the diaphragmthereby affecting both pressure settings.

FIG. 2 shows an alternate calibration-stop member 82 comprising firstouter annular portion 84 joined to second inner annular portion 86 byland 88 formed with isolation groove 90 therebetween. Aperture 92 isprovided to permit pin 16 to pass therethrough. Member 82 isparticularly useful when it is desirable to provide a narrower pressuredifferential since portion 86 is virtually on the same level as outerportion 84 prior to calibration- Although the invention has beendescribed with respect to a specific preferred embodiment thereof, manyvariations and modifications will immediately become apparent to thoseskilled in the art. It is therefore the intention that the appendedclaims be interpreted as broadly as possible in view of the prior art toinclude all such variations and modifications.

I claim:

1. A condition responsive device comprising a circular snap-actingdiaphragm having a dished surface movable to and from first and secondovercenter configurations;

calibration means including a member having first and second portions,and means separating the first and second portions so that the secondportion can be deformed without affecting the first portion, the memberpositioned adjacent a surface of the diaphragm; and

actuation means positioned adjacent the diaphragm and responsivethereto, the actuation means in contact with the diaphragm when thediaphragm is in the first configuration and out of contact with thediaphragm when the diaphragm is in the second configuration.

2. A device according to claim 1 in which the first portion of themember is a relatively stiff annular flange, the second portion of themember is a relatively thin flange, and the means separating the twoportions from each other includes an isolation groove defined in themember between the portions.

3. A condition responsive assembly comprising a generally circulardiaphragm deformed into a dished shape to render it snap acting from afirst configuration to a second opposite configuration upon theoccurrence of the condition,

a calibration-stop member comprising a first relatively rigid annularflange portion, the periphery of the diaphragm and the flange beinggenerally coincident and attached to one another, the member having asecond relatively flexible portion extending radially inwardly from theflange portion, and means separating the first and second portions sothat the second portion can be deformed without affecting the firstportion.

4. An assembly according to claim 3 in which the means separating thefirst and second portions is a circular groove.

5. An assembly according to claim 4 further including a first chamberformed on the side of the diaphragm remote from the calibrationstop-member, a port formed in the first chamber to permit ingress andegress of a fluid medium, and means mounted adjacent the diaphragm onthe side of the diaphragm opposite the first chamber responsive to thesnapping of the diaphragm from one configuration to the other upon theoccurrence of a predetermined pressure in the first chamber.

6. An assembly according to claim 5 in which the means responsive to thesnapping of the diaphragm from one configuration to the other includesan electric switch comprising a base member having an open end, astationary contact and a movable contact arm disposed in the base, themovable arm adapted to move into and out of engagement with thestationary contact, a hub having a bore extending therethrough closingthe open end of the base, an aperture provided in the calibration-stopmember and a motion transfer pin slidably received in the bore of thehub extending from the movable contact arm through the aperture in thecalibration-stop member to a point adjacent the diaphragm so that in oneconfiguration of the diaphragm the movable contact arm is separated fromthe stationary contact.

7. An assembly according to claim 6 in which two electrical leads extendfrom the electrical switch, a casing is disposed about the electricalswitch and is provided with two apertures through which the leadsextend, and electrically insulative potting material fills the spacebetween the casing and the switch and leads.

8. An assembly according to claim 3 in which the second portion of thecalibration-stop member is annular in shape and is thinner than thefirst flange portion and a land and groove separate the two portionsfrom one another.

9. An assembly according to claim 8 in which the second portion of thecalibration-stop member is conical in shape.

10. An assembly according to claim 7 including a port fitting positionedin the port of the first chamber, the fitting having a threaded bore, atubular threaded member adjustably positioned in the bore of the fittingand a coil spring extending between the tubular threaded member and thediaphragm.

1. A condition responsive device comprising a circular snapactingdiaphragm having a dished surface movable to and from first and secondovercenter configurations; calibration means including a member havingfirst and second portions, and means separating the first and secondportions so that the second portion can be deformed without affectingthe first portion, the member positioned adjacent a surface of thediaphragm; and actuation means positioned adjacent the diaphragm andresponsive thereto, the actuation means in contact with the diaphragmwhen the diaphragm is in the first configuration and out of contact withthe diaphragm when the diaphragm is in the second configuration.
 2. Adevice according to claim 1 in which the first portion of the member isa relatively stiff annular flange, the second portion of the member is arelatively thin flange, and the means separating the two portions fromeach other includes an isolation groove defined in the member betweenthe portions.
 3. A condition responsive assembly comprising a generallycircular diaphragm deformed into a dished shape to render it snap actingfrom a first configuration to a second opposite configuration upon theoccurrence of the condition, a calibration-stop member comprising afirst relatively rigid annular flange portion, the periphery of thediaphragm and the flange being generally coincident and attached to oneanother, the member having a second relatively flexible portionextending radially inwardly from the flange portion, and meansseparating the first and second portions so that the second portion canbe deformed without affecting the first portion.
 4. An assemblyaccording to claim 3 in which the means separating the first and secondportions is a circular groove.
 5. An assembly according to claim 4further including a first chamber formed on the side of the diaphragmremote from the calibration stop-member, a port formed in the firstchamber to permit ingress and egress of a fluid medium, and meansmounted adjacent the diaphragm on the side of the diaphragm opposite thefirst chamber responsive to the snapping of the diaphragm from oneconfiguration to the other upon the occurrence of a predeterminedpressure in the first chamber.
 6. An assembly according to claim 5 inwhich the means responsive to the snapping of the diaphragm from oneconfiguration to the other includes an electric switch comprising a basemember having an open end, a stationary contact and a movable contactarm disposed in the base, the movable arm adapted to move into and outof engagement with the stationary contact, a hub having a bore extendingtherethrough closing the open end of the base, an aperture provided inthe calibration-stop member and a motion transfer pin slidably receivedin the bore of the hub extending from the movable contact arm throughthe aperture in the calibration-stop member to a point adjacent thediaphragm so that in one configuration of the diaphragm the movablecontact arm is separated from the stationary contact.
 7. An assemblyaccording to claim 6 in which two electrical leads extend from theelectrical switch, a casing is disposed about the electrical switch andis provided with two apertures through which the leads extend, andelectrically insulative potting material fills the space between thecasing and the switch and leads.
 8. An assembly according to claim 3 inwhich the second portion of the calibration-stop member is annular inshape and is thinner than the first flange portion and a land and grooveseparate the two portions from one another.
 9. An assembly according toclaim 8 in which the second portion of the calibration-stop member isconical in shape.
 10. An assembly according to claim 7 including a portfitting positioned in the port of the first chamber, the fitting havinga threaded bore, a tubular threaded member adjustably poSitioned in thebore of the fitting and a coil spring extending between the tubularthreaded member and the diaphragm.